The present invention relates to a gas tank arrangement for an internal combustion engine. The invention also relates to a vehicle comprising such a gas tank arrangement. The invention is applicable on vehicles, in particularly low, medium and heavy duty vehicles commonly referred to as trucks. Although the invention will mainly be described in relation to a truck it may also be applicable for other types of vehicles such as e.g. working machines, cars, etc.
In relation to propulsion systems for heavy duty vehicles, internal combustion engines are frequently used. These internal combustion engines are most often propelled by a combustible fuel such as e.g. diesel or petrol. However, in order to further reduce engine emissions of the vehicles, alternative propulsion methods and/or fuels are being used, either alone or in combination with the well known combustible fuels. These may include, for example, ethanol or electrical propulsion from an electric machine, etc.
As a further alternative, a combustible gas, such as e.g. compressed natural gas, DME, biogas, etc. has been found a suitable propulsion fuel for vehicles in the form of trucks. The combustible gas can be used, either alone or in combination with a combustible fuel/liquid, for propelling the internal combustion engine. Since the residuals from the combustible gas are relatively environmentally friendly in comparison to e.g. combustible fuels, pollution from the emissions thereof are reduced for these types of engines.
A problem with engines being propelled by the above described combustible gas is that if leakage of gas occurs from e.g. the gas tank or other positions of the system prior to combustion thereof, there is a risk of green house gas emission pollution. Unwanted leakage of this kind also has an economical aspect since the fuel consumption will increase. There is thus a need to further improve the gas tank arrangements for these internal combustion engines.
It is desirable to provide a gas tank arrangement which at least partially overcomes the deficiencies of the prior art.
According to a first aspect of the present invention, there is provided a gas tank arrangement for an internal combustion engine, the gas tank arrangement comprising a gas tank configured to contain a combustible gas, and a first additional gas tank positioned in downstream fluid communication with the gas tank, wherein the gas tank arrangement further comprises a second additional gas tank positioned in downstream fluid communication with the gas tank and in upstream fluid communication with the first additional gas tank.
The wording “combustible gas” should in the following and throughout the entire description be interpreted as a gas which can be ignited, either self-ignited by compression or be ignited by e.g. a spark plug. The invention should thus not be limited to any specific combustible gas. However, as a non-limiting example, the combustible gas may be natural gas, which is described further below. Other alternatives are also conceivable such as e.g. H2, DME, biogas, gaseous hydrocarbons, etc. The combustible gas can be in liquid phase and in gas phase. Hence, the wording “combustible gas” should be interpreted to include liquefied gas as well as gas in gas phase.
An advantage of the present invention is that the fuel consumption of the internal combustion engine is improved. The reason is that prior to refill of the gas tank, the pressure level of the gas tank can be reduced by delivery of combustible gas to the second additional gas tank instead of venting the gas tank and deliver excess gas to e.g. the tank station or to the ambient environment. Hence, substantially all the combustible gas in the gas tank can be delivered to the internal combustion engine for combustion thereof during operation of the vehicle. Accordingly, excess gas can be delivered to the second additional gas tank when venting the gas tank. The gas tank arrangement is thus more environmentally friendly since excess gas from the gas tank can be stored in the second additional gas tank instead of ventilation to the ambient environment. The energy efficiency is also improved since the fuel consumption will be reduced. The first and second additional gas tanks may thus be arranged downstream the gas tank by means of separate conduits.
According to an example embodiment, the first additional gas tank may be configured to be positioned in upstream fluid communication with the internal combustion.
Hereby, combustible gas is provided to the internal combustion engine from the first additional gas tank. The first additional gas tank may be arranged in fluid communication with a fuel injection system of the internal combustion engine as will be described further below.
According to an example embodiment, the gas tank arrangement may comprise a compressor positioned in fluid communication between the first and second additional gas tanks.
The compressor may be arranged to compress combustible gas in gas phase into high pressure combustible gas in gas phase, which high-pressure gas is delivered to the first additional gas tank. Hereby, the second additional gas tank can be arranged as a low pressure gas tank adapted to contain combustible gas having a relatively low pressure level in comparison to the pressure level of the combustible gas in the first additional gas tank.
According to an example embodiment, the compressor may be a mechanically driven gas compressor connectable to the internal combustion engine.
The gas compressor may be connected to the internal combustion engine via e.g. an engine power take off system or a gearbox power take off system of the vehicle. An advantage is that the gas compressor can be propelled by means of brake energy from the vehicle. Accordingly, the mechanically controlled gas compressor can be energized by utilizing the kinetic energy of the vehicle driveline.
According to an example embodiment, the compressor may be an electrically driven gas compressor.
An electrically driven gas compressor is beneficial in situations where the vehicle is driven at relatively long straight ahead roadways where no braking action is likely to occur, or the vehicle is less likely to be driven downhill for regeneration of energy. An electrically driven gas compressor is also beneficially used when the vehicle is standing still during, for example, refill of the gas tank. An electrically controlled gas compressor can be beneficial since there is further freedom at which position of the vehicle it can be arranged.
According to an example embodiment, the gas tank arrangement may further comprise a valve positioned in fluid communication between the first and second additional gas tanks, wherein the first additional gas tank is positioned in upstream fluid communication with the second additional gas tank via the valve.
Hereby, combustible gas is allowed to be controllably delivered from the first additional gas tank back to the second additional gas tank. This may be beneficial in cases when the gas pressure in the first addition gas tank exceeds a maximum allowable pressure limit. In such case, the first additional gas tank can be vented by positioning the valve in an open position to allow combustible gas to be delivered back to the second additional gas tank. Hence, the valve may be arranged at a separate conduit between the first and second additional gas tanks, i.e. two conduits may be arranged between the first and second additional gas tanks. A further advantage of the valve is that it enables for an open conduit back to the second additional gas tank when, for example, the engine is shut off and there is a desire to reduce the pressure in the conduits of the gas tank arrangement. The valve may be an electrically controlled valve or a pressure relief valve.
According to an example embodiment, the gas tank arrangement may comprise a gas converter arrangement arranged to convert liquefied combustible gas to compressed combustible gas, the gas converter arrangement being positioned in fluid communication between the gas tank and the first additional gas tank.
Hereby, the combustible gas can be provided in liquid phase from the gas tank and thereafter converted into pressurized gas phase before being delivered to the first additional gas tank. The pressurized gas is suitable for delivery to a fuel injection system of the internal combustion engine.
According to an example embodiment, the gas converter arrangement may comprise a fuel pump and an evaporating unit positioned in downstream fluid communication with the fuel pump.
The fuel pump thus transports/delivers the liquid combustible gas to the evaporating unit, which compresses and converts the liquefied combustible gas into compressed combustible gas in gas phase prior to delivery to the first additional gas tank.
According to an example embodiment, the gas tank arrangement may comprise a first conduit arranged between the gas tank and the second additional gas tank.
According to an example embodiment, the gas tank arrangement may comprise a pressure relief valve arranged in the first conduit between the gas tank and the second additional gas tank.
Hereby, when the pressure in the gas tank exceeds a predetermined pressure level, the pressure relief valve is positioned in an open state to allow combustible gas to be delivered from the gas tank to the second additional gas tank. The pressure relief valve is thus controlled by means of the gas pressure in the gas tank. The pressure increase in the gas tank may be caused by e.g. a rise in gas tank temperature, etc.
According to an example embodiment, the gas tank arrangement may comprise a second conduit arranged between the gas tank and the second additional gas tank.
Accordingly, the first and second conduits are separate conduits. The gas tank and the second additional gas tank may thus, according to an example, be connected to each other by means of two separate conduits.
According to an example embodiment, the gas tank arrangement may comprise an electrically controlled valve arranged in the second conduit between the gas tank and the second additional gas tank.
Hereby, delivery of combustible gas from the gas tank to the second additional gas tank may be controlled by means of the electrically controlled valve. Combustible gas may thus be delivered to the second additional gas tank at situations other than when the gas pressure level of the gas tank exceeds a maximum threshold limit. The electrically controlled valve may, for example, be controlled to be positioned in an open state before the vehicle operator intends to refuel the gas tank. Hereby, excess gas in the gas tank is controllably delivered to the second additional gas tank, thus more combustible gas can be provided to the gas tank when refueling. Still further, a higher fill velocity of the second additional gas tank may be obtained by means of positioning both the electrically controlled valve and the pressure relief valve in an open state.
According to an example embodiment, the first additional gas tank may be a high pressure gas vessel configured to contain compressed combustible gas adapted to be delivered to a fuel injection system of the internal combustion engine.
Hereby, a storage tank for high-pressure combustible gas is provided which can deliver high-pressure combustible gas to the fuel injection system of the internal combustion engine when desired.
According to an example embodiment, the gas tank and the second additional gas tank may be configured to contain combustible gas of substantially similar pressure levels.
An advantage is that there is no need to pressurize the combustible gas before delivery to the second additional gas tank. Still further, if the gas pressure level of the second additional gas tank is slightly lower than the gas pressure level in the gas tank, there is no need to provide a pump or the like between the gas tank and the second additional gas tank for delivery of gas from the gas tank to the second additional gas tank, due to the difference in pressure levels.
According to an example embodiment, the combustible gas may be natural gas. Natural gas is a well known combustible gas which, at present, can be provided at a plurality of gas stations.
According to a second aspect of the present invention, there is provided a vehicle comprising an internal combustion engine and a gas tank arrangement according to any of the above described example embodiments of the first aspect of the present invention, wherein the internal combustion engine is arranged downstream the gas tank arrangement.
According to an example embodiment, the internal combustion engine may be a dual fuel internal combustion engine.
A dual fuel internal combustion engine should be understood to mean a combustion engine which can be propelled by both a combustible gas and a combustible fuel, or a mixture thereof. The combustible fuel may, for example, be diesel or petrol. However, the present invention should not be construed as limited to any specific alternative.
Further effects and features of this second aspect are largely analogous to those described above in relation to the first aspect of the present invention.
Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.